Docosahexaenoic acid (DHA) is a member of the omega-3 fatty acid family; it is found in all cell membranes, and is accumulated in especially large quantities in the retina and brain. Over the past decades, evidence has accumulated in support of the hypothesis that DHA may have an important role in pregnancy health and outcome, as well as in the postnatal development of perceptual and cognitive function in infancy. However, prior work on this topic has focused on postnatal supplementation and the amelioration of risk in premature infants; this is in contrast to evidence indicating that DHA is accumulated in the fetal brain during gestation, probably through maternal dietary intake. The current proposal is therefore based on the possibility that prenatal supplementation may be an especially efficacious means of affecting positive pregnancy and postnatal outcomes. An earlier clinical trial conducted by our research team provided a relatively low level of DHA supplementation (approximately 100 mg/day) during the last trimester of pregnancy. This supplementation produced an increase of 6 days in the duration of gestation. In addition, higher maternal RBC DHA at delivery in a subset of this population was related to infant cognitive outcomes (more mature infant attention and lower infant distractibility through 18 months of age). In the current application, we propose a Phase III Clinical Trial (randomized, double blind, placebo-controlled) with a larger supplement of DHA (600 mg/day vs 100 mg/day) and longer duration of supplementation (2 vs 1 trimester of pregnancy). This increased dosage and period of exposure is designed to increase gestation duration and intrauterine growth in the same population studied in the previous clinical trial. Reviewers of the initial submission felt the value of the study would be increased by infant followup. An extensive postnatal followup was included in the revision, designed to determine the effect of experimentally increasing maternal DHA intake on visual and cognitive outcomes in infancy and early childhood. Reviewers indicated approval of the added postnatal followup, however, they raised several new questions about compliance with capsule intake and possibly high attrition from the postnatal followup portion of the study and requested operational definitions of some measures. These have been addressed here in detail in the Introduction and body of the proposal.